Control circuit



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Y Z I p 1932- E. D. COOK 1,876,449 I CONTROL CIRCUIT Filed Aug. 8, 1928 3 Sheets-Sheet l Inventor: Ellsworth D. Cook His Attzf'ney 1 Sept. 6, 1932. E. D. cooK 1,876,449

' CONTROL cmcun' Filed Aug. 8, 1928 s Sheets-Sheet 2 Inventoh: El sworth D. CooK,

Hi5 Attorney Sept. 6, 1932. E. D. C OOK 1,876,449

CONTROL CIRCUIT Filed Aug. 8, 1928 3 Sheets-Sheet 3 Fig.6.

V 76 30 Inventor:

v v Elllswohth DPCooK, g; b His Attorney current to flow in 'sufiicient magnitude to per- Patented Sept. 6, 1932 U I-Tao sures PATENT orrlca ELLswonrn n. 0001, or scorn. m YORK, ASSIGNOB 'ro GENERAL ELECTRIC oomrm. A oonromnogw or NEW 1on1:

WMBOL CIRCUIT Applloattonjled August 8, 1928. Serial No. 298,821

My invention relates to control circuits and it deals more particularly with certain new and useful applications of self oscillatory circuits in connection with protective circuits, control circuits; and the like.

In Patent No.'1,696,566, issued December 25, 1928, of Emmett F. Carter, filed November 25, 1924, entitled High frequency duplex signaling system and which is assigned to the same assignee as the resent application, is disclosed an electron ischar e oscillation generator the operation of w ich is controlled in response to a control potential which is roduced b voice, or other signal, waves. his result is elfected by utilizing a second electron discharge device connected in the anode circuit of the oscillation genera- -tor, the grid of the second devicebeing normall biased negatively to a value such that insu icient anode'current flows to permit the generator to produce oscillations. By applying the control potential to the grid of this second, or control electron discharge device, the anode current, and hence, the operation of the oscillation generator may be efficiently and reliably controlled.

In accordance with one aspect of my present invention a coupling between the grid circuit of a control electron discharge device,

the above mentioned application, and the circuit of the oscillation generator, is provided whereby oscillations produced by the generator are supplied to the grid of the control device. Control potential is applied to the grid of the control device in the usual manner. When the control potential which is applied to the grid of the control device is of an order such that the impedance of that device is reduced sufiiciently to permit anode mit the production of oscillations, the oscillations produced are supplied back upon the grid of the control device. This, in turn, further reduces the impedance of the control device and increases,the anode current and the amplitude of the produced oscillations, this accumulative, or regenerative action continuing until the normal operatin conditions of the generator are reached, ependprovide means whereb which is utilized in the manner taught byrepresents a out upon the degree of coupling employed, as

'will later be explained, the oscillation geninvention to provide. While my invention deals particularly with the circuit as thus arranged, and as generally applied, it has among its further purposes to rovide means whereby a system of the type indicated may be applied to the operation of circuit interrupters, such as are used in power transmission lines and particularly to the automatic reclosing of such circuit interrupters when power is applied to the line and inresponse to line conditions.

A further purpose of the invention is to the oscillatory. circuits provided, as indicated above, may be utilized not only in the operation of the circuit interrupter but also inproducing signaling operations at a remote point indicating the condition of the switches. I

The novel features which I believe to characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of o eration, together with further objects an advantages thereof may best be understood by reference to the following description taken-in connection with the accompanying drawings in which Fig. 1 represents anembodiment of my invention; Fig. 2 represents certain operating characteristics of the circuit employed; Fig. 3 represents my invention applied toa particular ap lication; Fig. 4 represents a modifictaion; ig. 5'represents myinvention as applied to the automatic closing of circuit interrupters';'Fig. 6 represents a modification of the system shown in Fig. 5; Fig. 7 ower transmission line of the type to whic my invention may be advantageously applied and Fig. 8 represents signaling apparatus which may be utilized in connection with my invention.

Referring to Fig. 1 of the drawings I have shown at 1 an electron discharge device of the usual three element type which is connected in any well-known manner to produce oscillations. Connected to the anode circuit of the device 1 is a second electron discharge device 2 which is also of the three element type. The anode circuit of these devices extends from the negative side of a suitable source'of potential 3 through the cathode conductors of the discharge device 2, space between the cathode and anode of the device 2, conductor e', space between the cathode and anode of the device 1, choke coil 5, actuating winding of relay (3 to the positive side of the source of potential 3. The cathodes of the discharge devices 1 and 2 are energized by means of alternating current applied to the transformers 7 and 8 respectively. Connected between the grid and anode of the discharge device 1 is the usual oscillatory circuit 9. This oscillatory circuit is coupled to the grid of the control device 2 through a circuit extending through the secondary winding of a transformer 10, the primary winding of which comprises a part of the oscillatory circuit 9, secondary winding of a transformer 11, source of biasing potential 12, to the cathode of the control device 2. The source of potential 12 is of an order such that a negative potential is impressed upon the grid of the control device suflicient to preclude the flow of current in the anode circuit, or at least sufiicient to maintain this current at a value such that no oscillations are produced by the device 1.

The primary winding of the transformer 11 may be connected to any suitable source of control electromotive force. If the device is to be used in connection with the operation of overload circuit breakers this primary winding may be connected in shunt with an impedance 13 which is connected in series with the line to be protected. In such application of the system the relay 6 may be used to con trol the actuating winding of the circuit breaker.

As thus arranged when the potential across 'the impedance 13, and hence across the secondary winding of the transformer 11 increases beyond a certain value current will duced by the device 1. These oscillations will be supplied through the transformer 10 to the grid of the control device 2. This in turn additionally reduces the impedance of the device 2 and further increases the flow of anode current, thereby increasing the amplitude of the oscillations produced. This accumulative or regenerative action will continue until the 5 anode current has built up to its normal value and the oscillation generator 1 operates under normal conditions.

In the operation of my device it has been found that with a certain relatively close coupling between the windingsof the transformer 10 at a certain critical value of the control potential a very slight change in voltage across the impedance 13 will cause the anode current to build up practically instantaneously to its normal value, that is, sub- 'stantially square line action of this current may be had. In this manner relay 6, which may require a comparatively large current, may be reliably operated in almost instantaneous response to a very slight variation in the voltage across the impedance 13. With this coupling after the relay 6 has been operated it will be maintained in its energized condition by the regenerative connection between the oscillatory circuit 9 and the grid of the device 2.

With a degree of coupling less than the above mentioned certain relatively close coupling, the rate of increase of anode current with respect to the increase of applied control potential will be dependent upon the degree of coupling employed. This characteristic of the device is illustrated in Fig. 2

in which curves a and 5 represent the increase in anode current when the degree of coupling is less than that above mentioned, the curve 0 represents the static characteristics of the circuit and curve d represents the increase in anode current when the degree of coupling is either equal to or greater than that above mentioned. If the lesser degree of coupling be employed the anode current will decrease when the control potential is removed and the production of oscillations will cease whereas if a coupling corresponding to curve (2 be employed oscillations and hence the increased anode current will continue to flow notwithstanding that the control potential is removed.

In Fig. 3 I have shown my invention as applied to a limit switch in which an operating circuit is to be closed in response to a certain definite voltage and is to be opened in response to a different voltage. This use of my invention may be' advantageous in connection with the operation of oil burning furnaces in which an electric arc is used for ignition purposes and in which it is not safe to operate the furnace when the electric arc is not in operation. This system comprises two of the devices shown in Fig. 1, one of these devices 14 deriving its control electromotive force from a resistance 15 and the other of'these devices 16 deriving its control electromotive force from a resistance 17. The resistances 15 and 17 are connected in parallel across the are 20 of the ignition system of the furnace such that the potential of the arc is applied to-these resistances and a suitable portion of this potential is accordingly a plied to the grid of the control device of t e systems 14 and 16. The anode circuit of the oscillation generator 1' of the device 14 extends from the negative side of the source of potential 18 through a switch 19, space between the cathode and anode of control device 2, the space between the,cathode and anode of the oscillation generator 1', relay 6' to the positive side of the source of tential 18. A similar circuit ma be tr through corres onding elementso thedevice 16. The couphng between the windin of transformers 10' and 10 is greater t an the critical degree of couplin -mentioned above. The relays 6 and 6" 0% the respective devices 14 and 16 may be' utilized to control the energizing circuit of the motor 21 which drives the 'oil pump of the 'furnace. The contacts of the relay 6' are normallyopen-and the contacts of the relay 6" are normall closed. The taps on the resistances 15 an '17 are adjusted such that the relay 6 will operate at the lower limit of the voltage across the are 20 at which it is safe to operate the furnace and such that the relay 6" will operate at the upper limit of the voltage at which the furnace, may be safely operated.

As thus arranged if the otential across the are 20 exceeds the lower imit but does not exceed the upper limit, as during proper operation of the ignition system, 'the relay 6 will be energized and the relay 6" will be deenergized and the circuit of the motor 21 will be complete. If the voltage drops below the lower limit for any reason, as due to carbonizing of the electrodes, suflicient control electromotive force will not be applied to the grid of the device 2 to cause the oscillation generator 1 to produce oscillations. Since the anode circuit of'the devices 14 and 16 are periodically interrupted bythe rotating switch 19, the relay 6' and hence the motor 21 will then become deenergized. If the electrodes of the are 20 becomes s aced at too great a distance from each ot er for safe operation the potential on the resistance 17 will be increased sufliciently to trig er the device 16, thereby energizing the re ay 6" and deenergizing the motor 21.

If desired the? purpose of the rotating switch 19 may be accomplished by energizing the anode circuits of -the difi'erent discharge devices with alternating current, thatis, by

replacing the battery 18 with an alternating current generator. Since the' electron discharge oscillation generators 14 and. 16 can operate only when the anode, isat positive ployed in the arrangement shown in Fig. 6.

which will later be described. The relays 6' and 6" may be retained intheir'closed position during the inoperative half cycle either across the are over which the circuitof motor 21 is maintained closed may be varied to some extent by varying the coupling between these windings. This is apparent from Fig. 2. If it be assumed that the relays 6' and 6" operate upon a current of a certain value, as for example the dial X indicated in F i 2, it will appear that by varying the coup ing the relay will be operated in response to different values of control electromotive force. In Fig. 4 I have shown a modification of my invention as shown in Fig. 1 in that a single electron discharge device is employed. The electron discharge device 1 in this case is of the four element type having a pair of control grids 24 and 25. Connected between the control grid 24 and the anode 26 is the oscillatory circuit 9 including the transformer 10. The secondary-winding of the transformer 10 is connected in a circuit which extends from the control grid 25 through the secondary winding of the transformer 10, source of biasing potential 27, secondary winding of the transformer 11 to the cathode of the discharge device 1. The anode circuit of the device 1 extends from the anode 26, through choke coil 5, actuating winding of the relay 6 source of vpotential 29 7 and the cathode of the device 1. When suit able control potential has been applied to the grid of the discharge devicel through the transformer 11, sufiicient anode current will be caused to flow to permit the device to produce oscillations. These oscillations will be suppliedthrough the transformer 10 back upon the control electrode 25, thereby causing theanode current uickly to build up and maintaining the ano e current at a value suflicient to maintain the relay 6 in its energized condition, notwithstanding that the control potential is removed.

In Fig. 5 I'have shown my invention as applied to the automatic reclosing of'circuit breakers when power is applied to the line and in response to the conditions of the line. Since my device has the property of sensitive discrimination between potentials such as may be caused to result from varying impe ance of the line it has particular utility 1n this connection.

Referring to Fig. 5, I have shown a circuit interrupter 30which is included in a transthat shown in Fi 7, which is later to be described, and has t e characteristic that power may be supplied through the line in either direction. A suitable impedance 37 is con* nected in shunt with the contacts of the interrupter 30 so that a portion of the line potential is supplied to that part of the line on the opposite side of the interrupter from which the power is applied. Connected in shunt with the line 31, or between the line and ground, and upon opposite sides of the circuit interrupter 30, are a pair of transformers 32 and 33 which may comprise the usual distribution transformers of the system. Connected in circuit with the second-' ary winding of these transformers are the usual load circuits, not shown, and also the actuating windings of relays 34 and 35 respectively. These relays are arranged to control the energization and operation of the circuit 36 which is provided as indicated above for operating the circuit interrupter 30.

It is thought that this form of my invention will best be understood by reference to its operation. If it be assumed that power be supplied to the transmission line 31 at a point to the left of interrupter 30 it will be seen that full voltage will be ap lied to the relay 34 and that this relay will e actuated. Upon operation of this relay power will be supplied to an alternating current motor 49 through a circuit extending from the upper terminal of the secondary winding of transformer 32, through the lower contacts of interrupter 30, conductor 50, alternating current motor 49 and upper armature and upper contacts of relay 34 to the lower terminal of the'secondary winding of relay 34. The alternating current motor 49 drives a direct current generator 43 to energize the anode circuits of devices 1, 2 and 38, the cathode circuits of these devices being energized through transformers 51 the primaries of which are'connected in shunt with the alternating current motor 49.

The potential which appears across the secondary winding of transformer 33 will be dependent upon impedance conditions on the line 31 beyond the-transformer 33 and upon the circuit which is connected to the secondary winding of the transformer. If a heavy load, such as that of a lighting circuit, is connected to the line either through transformer 33 or other transformers to the right of switch 30 this potential will be very small and will approach that which would exist if a short circuit, or other low impedance fault, had occurred on the line. In accordance with my invention the circuit 36 is operated in response to the potential of this secondary winding to close the interrupter. By utilizing a coupling between the windings 10 which is greater than the critical coupling mentioned the circuit may be made to disnamue criminate between a. low im dance fault, and the low impedance condition caused by a ea stan ing that the impedances of the line under these conditions are but sli htly different. If a short circuit, or other low impedance fault condition exists upon the line beyond the transformer 33, or on the secondary load circuit of the transformer 33, potential which appears across the secondary winding of this transformer will not be sufficient to cause the production of oscillations and hence no further operation will result. I the impedance on the line be ond the interrupter 30, however, be but slightly greater as would be the case if a large load were connected to the line then suflicient potential will appear across the secondary winding of the transformer-33 to cause the operation of the equipment 36 and hence the closing of the circuit interrupter 30, this operation being as follows.

,The potential which appears across the secondary winding of the transformer 33 will be impressed upon the grid of an amplifier 38 through a circuit extending from the upper terminal of the transformer 33 through conductor 39, primary winding of transformer 40, a portionof resistance 41, upper armature and its lower contacts of relay 35 to the lower terminal of the secondary winding 33. It will be understood that this potential is not sufficiently great to" cause the actuation of the relay 35. This potential is amplified by the device 38 and supplied through transformer 42 and secondary winding of transformer 10 of the discharge device 1 to the grid of control device 2, these circuits being as indicated in Fig. 1. Oscillations will be produced by the device 1 and su plied to the grid of the device 2, causing fu l anodepurrent to immediately build up in the anode circuit of these devices, this circuit extends from the negative side of the source of potential 43 through smoothing reactor 44, space between the cathode and anode of the discharge device 2, space between the cathode and anode'of discharge device 1, choke coil 5, relay 6 to the positive side of the source of potential 43. Relay 6 will then be energized closing a circuit which extends from the u per terminal of the secondary winding of the transformer 32 through conductor 39, lower contacts of the circuit interrupter 30, actuating winding of relay 45, conductor 46, contacts of relay 6, conductor 47 conductor'48 and upper armature and its upper contacts of relay 34, to the opposite side of the secondary windingof transformer 32. Relay 45 .will then be operated closing a circuit which extends from the upper terminal of the secondary winding of the transformer 32 through the actuating winding of circuit in terrupter30, contacts of relay 45, conductor 48 and the upper armature and its upper contacts of relay 34 to the lower terminal of the load connected to the line notwithsecondary windin of transformer 32. Thus the actuating win 'ng of circuit interrupter 30 will be energized and the switch will be actuated to its closed position. Upon actua- 5 tion of the switch 30 to its closed position its lower contacts are open, thereby deenergizing the alternating current motor 49 and deenergizing the anode and cathode circuits of the devices 1 and 2.

"After the circuit interru ter 30 has been actuated to its closed position full potential will be applied across the primary of transformer 33, thereby actuating the relay 35 to its upper position. This operation interrupts the circuit of the primary of transformer 40 at the upper armature and lower contacts of relay 35 such that the high potential of the secondary winding of transformer 33 is not impressed upon this transformer.

The interrupter 30 may be retained in its closed osition, and operated to its open position, y any of the usual expedients which the well-known in the art.

If we assume that the interrupter 30 is in its open position and that power is supplied from the right-hand end of the line, relay 35 will be energized and relay 34' will be in its lower position. In closing its upper contacts relay 35 completes the circuit for the motor 49,'which extends from the up er tertacts of interrupter 30, conductor 50, alter nating current motor 49 and the primary winding of cathode transformers 51 in parallel, conductors 52 and 48, upper armature and its upper contact of relay 35 to the lower terminal of the secondary winding of transformer 33. The cathodes of the discharge devices will then be energized and themotor 49 will drive the direct current generator 43 4 to supplypower to the anodes of the different discharge devices. If the impedance of the line at the left of interru ter 30 be sufficiently great potential wi 1 be applied through the upper armature and its lower contacts of relay 34, a portion of resistance 41 and transformer 40 to the rid of the amplifier 38, such that when amp ified and a plied to the control device 2 through trans ormer 42 the device I will produceoscillations and cause the energization of the relay 6. I The interrupter will then be operated to its closed position as before thereby deenergizing the L circuits of the devices 1, 2 and 38, Operation of relay 34 will then protect the transf rmer 40 from the high otential of the secondary windingof trans ormer32.

It will be noticed that the device 1 produces oscillations until the circuit interrupt or hasbeenclosedi These. oscillations may, if desired, be su plied as. carrier currents to the transmision'lme by any suitable means.

As illustrated this means comprises/a pair 5 of coupling condensers 53, which are conminal of the secondary winding 0 trans-- former 33 through conductor 39, lower connected to the transmision line 31 on opposite sides of the interrupter 30. One terminal of each of these condensers is connected through the winding 54' which is in inductive relation with the oscillatory circuit of the oscillation generator 1 to ground. Thus during a predetermined time interval prior to the operation of the circuit breaker, high frequency oscillatory currents are supplied to the transmission line for transmislson in either direction. These'currents may be received at a remote point to indicate that the circuit breaker has operated. The interval during which these currents are produced may be made as long as desired by any suitable time delay mechanismwhich may be associated with the rela 6, for example, to retard its operation. f for some reason, as due to an inoperative condition of the switch 30 such as might result from faulty toggle mechanism, or the like, the circuit interrupter does not close after the relay 6 has been operated, it will be seen that carrier currents will be continuously supplied to the line, thereby indicating, in a manner later to be gescribed, that the switch is in faulty condiion.

.Figure 6 is-a modification of the circuit shown in Fig. 5. In this figure it will be noted thatthe transformers 32 and 33 are of the double secondary type. -It will further be noticed that the circuits of the electron discharge devices 1' and' 2 are energized by means of alternating current which is supplied through a transformer 55 having a plurality of secondary winding 56, 57, 58, 59 and 60. The winding 56 is utilized to ener- 'z e the-anode circuit of two assymmetricaly conducti electron discharge devices 61 and 62, whi d are connected to suppl direct current biasing potential to the gri of the control device 2. The winding 57supplies heating current to the cathodes of these devices. Thewindings 58 and 59 supply heating currents to the cathodes of the devices 2 and 1 respectively andthe winding 60 suppliespotential to the-anode circuits of these devices. Thus the anode circuit of the devices 1 and 2-extends fro v ductors of the device 2 through the space between the cathode and anode of this device, cathode conductors of the device 1, s ace bethe cathode con- I tween the cathode and anode of the evice 1,

choke coil 5 relay 6, and winding 60 to the cathode conductors of the device 2.

- Theoperation of this form of m j. inven. tion is as follows. If it be assumed t at end of the circuit and a portion of this potential will appear across the secondary winding of the transformer 33. This potential will besupplied through the lower contacts of relay 35 and transformer 40 to the grid of the controldevice 2. If the impedance conditions beyond the transformer 33 are such that the main contacts of the interrupter may properly be closed this potential will be sufficiently great to cause sufficient current to flow in the anode circuits of devices 1 and 2 to cause the device 1 to produce oscillations and the relay 6 to be operated. The operation of the relay 6 completes a circuit extending from the lower terminal of the secondary winding of the transformer 32, through conductor 46, contacts of relay 6, conductor 48, actuating winding of relay 45, conductor 63, lower armature and its upper contacts of relay 34 to the upper terminal of the secondary winding of transformer 32. Relay 45 will then close its contacts, thereby energizing, through an obvious circuit, the actuating windings of the interrupter 30, causing this interrupter to close its main contacts and to open its auxiliary contacts 64, thereby interrupting the supply of energy to the transformer 55, and the operation of the oscillator 1, The interrupter 30 will then be maintained in its closed position by mechanical or other means customarily employed in connection with switches utilized for this purose. p When power is supplied from the righthand end of the circuit it will be apparent that the operation of devices 1 and 2 is the same except that their operation is dependent upon line conditions beyond the transformer 32.

It will be noticed that the oscillation enerator of this Fi ure is similarly provlded with an output winding 54 which is adapted to apply high frequency currents through condensers 53 to the line for transmission in either direction.

Since the anode circuit of the oscillation generator is supplied with alternating potential it operates only during the portion of the alternating current cycle during which the anode is at positive'potential. Accordingly if the line impedance in the direction opposite to that from which power is supplied is such that oscillations are produced by the device 1 but this impedance is reduced, as due to trouble on the line, before sufficient time interval has elapsed to permit closing of the interrupter 30 the operation of the device 1 will beiinterrupted and the interrupter 30 will not be closed.

In Fig. 7 I have shown a transmission'circuit in connection with which my invention has particular utility. The transmission line comlprises a.loop.65. extending from a power station 66. Power may be supplied to either end of the loop through interrupter Q7 and 68. located at the station. Distributed about the loop are a plurality of interrupters is a high frequency responsive circuit, such as is shown in Fig. 8. The circuit is ofiany well-known construction employing an electron dischar e detector 7 2which isconnected to the line t rough a transformehZOv anda coupling condenser 71. Either the primary or secondary of this transformer, or, both may be tuned to the frequency of oscillations produced by the generators in the different devices 69. Connected in the output circuit of the electron discharge device 7 2 of thereceiving circuit is the actuating winding of an ordinary step by step selector switch having an armature 73 which .is adapted to be actuated over a bank of contacts 74 by means of a suitable ratchet and pawl arrangement of well-known form. Each contact 7 4; isconnected in circuit with a suitable signal lamp 75, and source of potential 7 6, such that when the armature 73 engages any one of these contacts a corresponding lamp .75 will be lighted. Also connected in the anode circuit ofthe rectifier 72 is a 'relay' 77"WlllCh is adapted when energized to close the circuit of a signal lamp .78 for a purpose later'tobe'indithe first and second interruptersfrom this end ofthe line are proper, one-interrupter'30 will be closed. Since a fault exists in the next section the. next interrupter will not close with the result that only one high freque'ncy impulse willbe supplied to the receiving apparatus associated with the left-hand end of'the' loop at the'station 66. The armature 73- of the selector switch ofthis apparatus will engage its first contact and cause the first one of the lamps 75 to be lighted.

'The operator will then close the switch "68 which is associated with the opposite end of the line. Since the impedance conditions in all of the sections to" the right of the section inark'ed X are correct four. "of the switches "30" will, be closed and the selector hich'is ass nted wiaithe right-hand end The operator is then informed thatt e fault lies between the second and third interrupt em from the left. If for any reason any of the switches does not clom notwithstanding that the impedance conditions in the direction opposite from that in which mer is supplied is correct, then high Thus for example if the operator observes 1 uency. currents from the oscillation nerator associated with that switch will continuously ing the relay 7 to be continuousl energized and the lamp 78 to be ligh loop circuit and-t e entire line is in good condition all of the switches will be closed. When the last switch closes, due to the fact that wer is supplied at both sides of the switc it will be seen that both of the relays 34 and 35 will be energized and will close their upper contacts. Resistances 41 pre vent the occurrence of a short circuit on transformers 32 and 33. When this occurs when these relays operate the circuit of the primary winding of the transformer is interrupted and the high potentials which exist upon the transformer windings 32 and 33 will be prevented from causing the circuit 36 3 to operate. The interrupter .30 will then be closed directly. The circuit of the actuating coil-of relay extending in the case shown in 5 from the upper terminal of the secon ary winding of transformer 33 through auxiliary contact 64 of the switch 30, actuating winding of relay 45, lower ar-'- mature and contacts of relay 34, lower armatures and contacts of relay 35, upper armature and its upper contacts of'relay 35 to v the lower terminal of the secondary winding 'of transformer Relay 45 will then be operated to connect the actuating winding of the interrupter 30 in shunt with the seconda windings of transformers 32 and 33.

the circuit shown in Fig. 6 the above 0 ration will be accomplished as follows. e actuating winding of the relay 45 will be energized through a circuit extending from the upper terminal, of transformer 33 through the lower armature and itspupper contacts of relay 35, conductor 63, actuating winding of relay 45, upper armature of relay 35, upper armature of relay 34 and conductor 46 to the lower terminal of the trans former 33. Relay 45 will then be actuated to connect the actuating winding'of interrupter 30in shunt with the secondary windings of transformers 32 and 33.

The embodiments of my invention shoi wn supplied to the line caus-' b current in another path, su ject' tionsto the first path and operating relay-ha as set forth in the appended claims.

What I claim asnew and desire to secure by Letters Patent of the United States, is:

. 1. In a system in which a control device is operated "in response to a voltage variation, and which includes a plurality of discharge ing from the spirit and scope of my invention paths connected in series, the method of opcrating said discharge paths which includes the ste said vo tage variation, producin oscillation;

sai first path to the oscillations produ controlling said device by current flowing through said discharge paths in series.

2. In a system in which a control device is operated in use to a voltage variation and which includes a plurality of series connected discharge paths, the method of 0 crating said disc arge paths comprising e of theimp'edance of one of P aths in-res use to said voltage variation thereby to increase the current in the circuit, producing electrical oscillations in response to said increase in current in the other, path, supplying said electrical oscillavice in response to the current in said circuit.

3. In combination, a pair of series connected electron discharge charge paths of said devices being connected in series, means for causing one of said dovicesto produce electric oscillations, for supp device to increase the current flowing therein, and means connected to nd to the current flowing through said a in series. clkdillli combinatfion, an e inu a pair 0 series co paths, means for controlling one of said di charge means for causing electrical oscillations to be produced responsively to current in the other discharge path, means for controllin the impedance of saidffirst patfi responsively to said oscillations and means connected to respond to current in said circuit. v

5. In combination, a relay, means for operating said relay comprising an electron disoscillation generator, the discharge path of said generator being connected in se rice with said relay, a second electron dis: charge device connected in series with said supplying otive force to said control of subjecting. one of said paths toand said de- I devices, the ,dis-.

means said oscillations to the othera control element, means for element to cause said 'enerator to operate,

and means for supplying oscillations produced by said generator to said control element thereby to control the flow of current through said relay.

6. In combination, an electron discharge oscillation generator having an oscillatory circuit, an electron discharge device having an anode, a cathode and a grid, said anode and cathode beingconnected in series with the anode circuit of said oscillation generator, means for supplying control electrometive force to said grid to control the operation of said oscillation generator, a variable coupling between said oscillatory circuit and said grid whereby oscillations produced by said generator are supplied to said grid, and a device to be controlled connected to respond to current flowing in said anode circuit.

In Witness whereof, I have hereunto set my I hand this 7th day of August, 1928. 1 ELLSWORTH D. COOK. 

